Method of separating foreign matter from a gas

Abstract

A hot gas cleaning and heat transfer method associated with a cooking hood assembly to separate foreign matter and liquids from gas moving through the hood assembly and transferring heat from the gas to a cooling liquid. A heat conducting wall surrounding a tubular passage accommodating a plurality of helical elements divide and direct gas into separate helical gas streams. The cooling liquid surrounds the wall to lower the temperature of the wall. Foreign matter, gas vapors, and liquids are separated from the hot gas into an annular sheath adjacent the heat conducting wall. The foreign matter, gas vapors, and liquid particles suspended in the gas are combined by mechanisms of centrifugal force, adhesion, condensation, and impaction. The gas vapors are condensed into liquid droplets. The liquid droplets, liquids, and foreign matter merge into a liquid film on the inside of the wall. This liquid film is moved down the wall and collected in an annular collecting member located adjacent the exit end of the wall. Clean gas flows through the annular collecting member to a desired location.

I claim: 
     
       1. A method of removing foreign matter from a hot gas and transferring heat from the gas to a first liquid comprising: moving hot gas, gas vapors, and foreign matter carried by hot gas in a spiral flow path in a passage through an elongated cylindrical wall having a gas entrance end and a gas exit end open to said passage to provide an annular sheath of hot gas, gas vapors, and foreign matter adjacent the cylindrical wall, introducing a second liquid into the gas entrance end of said passage during the flow of gas and foreign matter carried by the gas in said passage, said second liquid being collected on said wall and carried from said wall by the annular sheath of gas, dividing the hot gas and second liquid and foreign matter carried by the gas into separate gas streams during the flow thereof in said passage, lowering the temperature of the hot gas in said annular sheath adjacent said cylindrical wall by moving said second liquid in a chamber around said cylindrical wall thereby cooling said wall, transferring heat from the hot gas in said annular sheath of gas to said second liquid thereby lowering the temperature of said hot gas, gas vapors, and foreign matter in said annular sheath of gas, condensing gas vapors moving with said annular sheath of gas into liquid droplets, merging the liquid droplets into a liquid film with said first liquid introduced into said passage, collecting foreign matter including the liquid film, carried by the gas on the said wall during the flow of gas through said passage, separating the annular sheath of gas, liquid film, and foreign matter discharged from the exit end of the wall from a stream of gas surrounded by said annular sheath of gas, and moving said second liquid to and from said cooling chamber to cool said wall with said second liquid in the chamber. 
     
     
       2. A method of removing foreign matter from a hot gas and transferring heat from the gas to a fluid comprising: moving hot gas, gas vapors, and foreign matter carried by the hot gas in a spiral flow path in a passage through an elongated cylindrical wall having gas entrance and gas exit ends open to said passage to provide an annular sheath of hot gas, gas vapors, and foreign matter adjacent said cylindrical wall, introducing liquid into the gas entrance end of said passage during the flow of gas and foreign matter carried by the gas in said passage, said liquid being joined with the annular sheath of hot gas, gas vapors, and foreign matter and collected on said cylindrical wall, lowering the temperature of the liquid, hot gas, gas vapors, and foreign matter adjacent said cylindrical wall by moving a cooling fluid in a chamber around said wall thereby cooling said wall and transferring heat from said hot gas, gas vapors, and foreign matter to said fluid, condensing gas vapors moving in said annular sheath of gas through said passage adjacent said wall into liquid droplets, merging the liquid droplets into a liquid film, collecting foreign matter, including the liquid film carried by the gas on said wall during the flow of gas through said passage, separating the annular sheath of gas, liquid film, and foreign matter discharged from the exit end of the wall from a stream of gas surrounded by said annular sheath of gas, collecting condensed liquid and foreign matter discharged from the exit end of said wall, and moving the fluid through said chamber. 
     
     
       3. The method of claim 2 wherein: the gas, gas vapors, and foreign matter carried by the gas are divided into separate gas streams with a plurality of end-to-end helical elements located in said passage. 
     
     
       4. The method of claim 2 wherein: the gas is drawn through said passage by means located downstream of the wall. 
     
     
       5. The method of claim 2 wherein: the gas and foreign matter carried by the gas are divided into separate gas streams with a plurality of end-to-end helical elements located in said passage, and including moving the fluid around said wall to cool said wall with said fluid, thereby cooling the gas in the passage. 
     
     
       6. The method of claim 5 wherein: the fluid is moved in a generally spiral path around said wall. 
     
     
       7. The method of claim 2 wherein: the cylindrical wall is cooled with a cooling liquid. 
     
     
       8. The method of claim 7 including: moving said cooling liquid relative to said wall during the cooling of said wall. 
     
     
       9. The method of claim 7 including: moving said cooling liquid in a generally spiral path relative to said wall during the cooling of said wall.